1. Field of the Invention
The present invention refers in general to a fluid conveyance and/or distribution device with ring nut coupling and in particular to a hydraulic valve with ring nut coupling, for example in fluid conveyance and distribution systems.
2. Description of the Related Art
In order to optimise and economise the production of fluid conveyance and distribution systems, for example hydraulic circuits, provided with pipes and valves of various types, for example distribution valves, control valves, exhaust valves, damping valves, delivery valves or selector valves, the valves are integrally produced independent of the piping and connected thereto only when assembling the hydraulic circuit.
During the assembly, for example of a hydraulic circuit, the valves and piping are connected to each other so as to allow the execution of the desired functions.
For such purpose, the valve usually comprises an externally threaded coupling portion and a ring nut with inner threading, adapted to be screwed on the coupling portion in order to maintain one end of a pipe in engagement with this coupling portion.
This type of connection has the disadvantage lying in the fact that both the tightening of the ring nut during assembly and the loosening of the ring nut during maintenance or replacement of the valve require a specific space around the ring nut in order to be able to grasp it with the hand or with a tightening tool. Nevertheless, this need for space for mounting and dismounting the flow control valves and devices in general is difficult to reconcile with the very narrow spaces of the industrial plants, civilian or military, in which the fluid conveyance and distribution systems are integrated. Actually, in most plants, the only freely accessible part of a valve is the control portion thereof, for example a handle for regulating the flow through the valve and it is the same control handle which further blocks access to the coupling ring nuts.
A further disadvantage of the valves of the prior art lies in the poor reproducibility of the tightening torques of the ring nuts most suitable for the ideal operation of the valve. This also applies in the case of tightening the support rings for a sealed positioning of the shutter, for example a ball shutter, inside the valve body. Actually, depending on the application, the maintenance programs for fluid distribution systems provide for the complete dismounting of the valves, cleaning the single components and the subsequent reassembly of the cleaned valves at three-month or yearly maintenance intervals for example.